chapter 5 turbulent diffusion flames - FedOA

sections of gaseous

sections of gaseous compounds at 213 nm at their concentrations and temperatures in the flames as estimated by numerical modeling. Fig. 3.36 Scattering in Flame A at X/D=23 (a) and X/D=115 (b). �QVV ; + QVV; __ gas-phase scattering. At X/D=23, the scattering signal reaches a peak value at about r/R=4 (Fig.3.34 a). The scattering signal is of the same order of magnitude of the gas species scattering but it clearly exceeds this value; excess scattering (ΔQVV), also reported in the figure, peaks roughly in correspondence with the maximum fluorescence signal (Fig.3.34 a). Scattering cross section increases by more than one order of magnitude from X/D=23 to X/D=115 (Fig.3.36 b) and in this case it is much higher than the gas-species scattering. At this flame location, both LII and LIF signals are detected with a prevalence of incandescence of 94

particles over the fluorescence of molecular compounds. The same behavior is shown by Flame B (Fig.3.37). The first flame location (X/D=10) is characterized by the complete absence of incandescence signal and the presence of a LIF signal which maximizes at r/R=2.7 (Fig.3.35 a). The measured scattering signal is quite low; it has a maximum value at the flame centerline and decreases moving towards the outer flame zones. Fig. 3.37 Scattering in Flame B at X/D=10 (a) and X/D=100 (b). �QVV ; + QVV; __ gasphase scattering. The estimated contribution of gaseous compounds to the scattering is of the same order of magnitude of the measured scattering signal at the flame centerline but decreases by one order of magnitude at increasing radial locations. As a result, the excess scattering profile maximizes in correspondence with the maximum intensity of the LIF signal (Fig.3.37 a). 95